The present invention relates to an ion-conducting composite electrolyte membrane and a fuel cell using the same.
Since fuel cells converting chemical energy into electrical energy are efficient, and do not produce environmental pollutants, the fuel cells have drawn attention as clean power supplies for portable information devices, household use, vehicles, and the like, and the development of the fuel cells have been promoted.
There are various types of fuel cells classified according to the kinds of used electrolytes, and in particular, a fuel cell using an organic material such as methanol or hydrogen as a fuel has drawn attention. Important constituent elements determining the output performance of such a fuel cell include an electrolyte, an electrolyte membrane, a catalyst membrane, and a membrane-electrode assembly (MEA) formed by sandwiching an electrolyte membrane between catalyst membranes. For example, various types of electrolytes have been developed, and an electrolyte made of a perfluorosulfonic-acid-based resin is a representative example, and is considered superior in durability and performance.
The important constituent elements of the fuel cell determine not only output performance of the fuel cell, but also reliability and durability for ensuring a long-term stable operation, and the important constituent elements also relate to productivity thereof, and exert an influence on manufacturing efficiency and production cost. Various methods for an improvement in performance of an electrolyte membrane have been reported.
The electrolyte membrane is used to form a membrane-electrode assembly (MEA), and a unit cell is configured with use of the membrane-electrode assembly; therefore, the electrolyte membrane is used in a stack type fuel cell in which a plurality of unit cells are stacked, and are connected to one another in series, or a planar stack type fuel cell in which a plurality of unit cells are arranged in a planar form, and are connected to one another in series.
A large number of methods of forming an electrolyte membrane used in a fuel cell have been reported (refer to the following PTLs 1 to 5).
For example, in the following PTL 1 entitled “proton conductive complex and its method for manufacture, and electrochemical device”, there is described “a proton conductive complex which is formed by mixing a carbon cluster including a proton dissociative functional group, and a polymer material having resistance to permeation of water and/or liquid molecules such as alcohol molecules, and includes the polymer material at a mixing ratio of larger than 15 mass % to 95 mass % inclusive (more specifically at a mixing ratio of 20 mass % to 90 mass % both inclusive).
It is to be noted that a proton-conducting polymer using a fullerene C60 is known (refer to the following PTLs 1 and 6), and the above-described planar stack type fuel cell is described in, for example, the following PTL 7.